Sets were for use on the government's AUTOVON (AUTOmatic VOice Network)
system, which connected sites worldwide. It's key features
include the ability to use 4-wire connections to minimize echo on long
distance connections, the use of priority codes to give preference to
higher priority communications when the system was operating at
capacity, "hot line" dialing and conferencing. A brief overview
of the system may be found in "Bell
Laboratories Record," April 1968. An internet search on
AUTOVON will provide more technical details and background information.

The appropriate priority code
was dialed with an "important" call, such as a command and control
call. If needed, calls starting with routine level and going up
to the level below the dialed level were preempted. The lower
priority users got a tone sequence indicating their call was being
preempted.

Standard 500 and 2500-series sets were used for routine callers, who
did not have the need or authority to preempt other callers. They
may be found on other pages of this site (see links above).

BSPs for Autovon sets were moved from
division 502 to division 529 when it was created for
"Station Apparatus and Equipment intended solely for
specially-engineered lines, not for general telephone use." This
happened sometime before the publication of the 10/68 division 502
index.

This information is hard to find, as the BSPs and technical data were
not generally distributed.
Later division indexes had a heart icon next to the BSPs, indicating:"a new or reissued item which, because of its limited need,
will not be
distributed on standing order
except through coded distribution.
Additional copies may be obtained by placing regular (one-time) orders."
This page is intended to be a quick summary of the models produced and
major functions. Western catalogs and technical documentation
only show the models that were in production or service at the
publication date. To understand the full scope of models produced
we must compile data from many years of documents.

Each model had suffix letters that defined variations.
Details can be
found in the Bell System technical documentation (e.g. BSPs - Bell
System Practices).

Most info in the chart is from manufacturer catalogs and ads
plus discussions on the ATCA and TCI listservs. No claim is
made regarding accuracy or completeness.

For more information, see my article "Top Secret Telephones,"
the cover story in the April 2011 issue of TCI's Singing Wires,
and search for Autovon in the TCI Library. www.telephonecollectors.info/

If you're enjoying looking at this level of detail and haven't joined
one of the phone clubs yet, see the links page.

If you're identifying
a phone, you still need to check the internal
components as many phones were refurbed and had internal components
changed or removed. If done in a Bell System refurb facility, the
code on the bottom was usually repainted or remarked. Many
independent shops or field mods were not remarked with the accurate
model number.

When buying sets, watch out for standard phones that have been modified
to look like Autovon sets, by replacing the dial and faceplate.
While these look like proper sets to the casual observer, closer
scrutiny will generally show the lack of a ringer control on the left
side (sets with N1A ringer), the
required 4-wire circuitry inside and the proper markings on the bottom
plate.

As with the 500 seeries, a W suffix indicates sets made without Bell
System markings, and M indicates a Modular set.
More details on set coding are found on the 500-series
page.